This invention relates generally to valves useful in reservoir and well testing and other operations from a floating drilling or workover vessel. It relates specifically to a combination lubricator and retainer valve which may selectively prevent fluid flow in one or both directions in order to prevent inadvertent escape of fluids into the environment and to allow for a chamber within the test or work string for the introduction and running of various downhole tools.
Generally when it is desired to determine the well or reservoir potential of a well drilled in offshore waters from a floating drilling vessel, tubing is run from the vessel to the producing formation that requires testing. Surrounding this tubing from the drilling vessel to the sea floor is a device called a riser which aids in preventing inadvertent escape of formation or other fluids into the environment. Below the riser is a blowout preventer stack to prevent the flow of downhole fluids to the surface, if necessary. The lower end of the tubing is usually connected to various testing devices and the upper end is connected either to a flow diversion device which diverts the flow of formation fluids to certain surface test and storage equipment or is connected to a pressure containment device such as a wireline stuffing box which allows the introduction of wireline into the tubing while the tubing is pressurized within from formation fluids.
Typically, there is also connected to the tubing string a master valve generally referred to as a subsea test tree (SSTT). The subsea test tree is a remotely controlled device to prevent the flow of formation fluids to the environment in case the drilling vessel has to move from the well site in an emergency such as a severe storm. The tubing string above the SSTT may be unlatched from the top of the SSTT by an integral part of the SSTT, leaving the lower portion of the SSTT within the blowout preventer stack. The lower portion of the test string is supported by the SSTT which in turn is supported by a landing device within the wellhead.
When the upper test string of tubing is unlatched from the SSTT, the upper test tubing may contain pressurized formation fluids which could escape into the environment if not contained in some manner. In the past these fluids have been prevented from escaping by a retainer valve which would prevent pressure fluid from escaping.
Another device typically connected to the test string of tubing was a lubricator which would allow the introduction of a wireline tool string or other devices into the test string. If this lubricator section was placed above the drill floor of the drilling vessel, it often was quite a height above the normal personnel working surface and difficult to manipulate.
A lubricator valve was developed that could be placed below the drill floor at a preselected depth within the riser. This device contained a method of preventing the flow of formation fluids to the surface through the flow path of the tubing and once closed would allow the pressurized fluids above the lubricator valve to be bled off and the tubing string above the lubricator valve to be used for the introduction of tools into the tubing eliminating the awkward lubricator and tubing above the drill floor.
Both the above mentioned lubricator and retainer valve were remotely controlled from the drilling vessel by hydraulic pressure applied through hydraulic lines. As can be seen above, two different valves were used along with their associated operating equipment to perform the required functions. It is desirable to incorporate the two valves into one valve that will perform both functions. The present invention is a combination lubricator and retainer valve which is constructed to failsafe and to selectively prevent the flow of fluids in one or both directions, yet still allow, in an emergency situation, for "kill" fluids to be pumped through the valve to "kill" the well.
U.S. Pat. No. 4,197,879 discloses a lubricator valve similar to other such devices. This valve shows a rotating ball that does not move longitudinally and holds pressure from below. However, unlike the present invention which hydraulically fails in the closed position preventing upward fluid flow, the '879 valve will remain in either the open or closed position upon failure of its actuator system. Therefore, if it hydraulically fails in the open position, the valve remains in the open position and will not prevent the escape of fluids into the environment. The present invention may utilize positive control line pressure to remain open and upon loss of such control line pressure the valve will close.
U.S. Pat. No. 4,253,525 discloses a retainer valve that hydraulically fails in the open position allowing the passage of fluids by the valve and into the environment. The '525 valve will hold pressure from either direction if closed. However, once in the closed position, the valve will not allow "kill" fluids to be pumped through the valve.